<?php

declare(strict_types=1);

namespace Mironsoft\Loyalty\Model\Customer\Attribute\Backend;

use Magento\Eav\Model\Entity\Attribute\Backend\AbstractBackend;
use Magento\Framework\Event\ManagerInterface;
use Mironsoft\Loyalty\Model\Config\LoyaltyConfig;
use Mironsoft\Loyalty\Model\Service\PointsCalculator;

/**
 * Recalculates loyalty_tier on save (chapter 26) and, new in chapter 35, notifies
 * other modules of an actual tier change via a custom event.
 */
class LoyaltyTierBackend extends AbstractBackend
{
    public const EVENT_TIER_CHANGED = 'mironsoft_loyalty_customer_tier_changed';

    /**
     * @param PointsCalculator $pointsCalculator Pure business rule for determining a tier from a point total.
     * @param LoyaltyConfig $loyaltyConfig Typed reader for the tier_thresholds configuration value.
     * @param ManagerInterface $eventManager Dispatches EVENT_TIER_CHANGED for other modules to observe.
     */
    public function __construct(
        private readonly PointsCalculator $pointsCalculator,
        private readonly LoyaltyConfig $loyaltyConfig,
        private readonly ManagerInterface $eventManager
    ) {
    }

    /**
     * Overwrites loyalty_tier with a freshly calculated value and dispatches
     * EVENT_TIER_CHANGED when the recalculated value actually differs from the
     * value the entity held before this save. $object deliberately carries no
     * native type hint, unchanged from chapter 26's contravariance explanation.
     *
     * @param \Magento\Framework\DataObject $object The entity currently being saved (a Customer model here).
     * @return $this
     */
    public function beforeSave($object)
    {
        $previousTier = $object->getOrigData($this->getAttribute()->getAttributeCode());
        $pointsBalance = (int) $object->getData('loyalty_points_balance');

        $tier = $this->pointsCalculator->determineTier(
            $pointsBalance,
            $this->loyaltyConfig->getTierThresholdsJson()
        );

        $object->setData($this->getAttribute()->getAttributeCode(), $tier);

        if ($previousTier !== null && $previousTier !== $tier) {
            $this->eventManager->dispatch(self::EVENT_TIER_CHANGED, [
                'customer' => $object,
                'previous_tier' => $previousTier,
                'new_tier' => $tier,
            ]);
        }

        return parent::beforeSave($object);
    }
}